Case Study Demonstrating the Ability of 3D3C Seismic to Predict Natural Fractures and Petrophysical Properties of Shale

Harris, Ron¹; Tinnin, John²
¹Anadarko Petroluem, The Woodlands, TX.
²ION Geophysical/ GX Technologies, Houston, TX.

Introduction
The Devonian age Marcellus is a major shale play in North America that has drawn international attention. The Marcellus is believed to have the potential to become the second largest gas field in the world. Commerciality was established in 2004 with the majority of these wells are drilled as horizontal wells with laterals 1 to 2 kilometers in length. Hydraulic fracturing is required to stimulate a sufficient volume of shale that will produce commercial quantities of natural gas. Within the study area, the Marcellus is approximately 60 meters thick and buried at a depth of 2.6 kilometers.

The challenges of this play include:
1) identifying shale ‘sweet spots' which represent areas of higher productivity and driven by several petrophysical properties including porosity, permeability, brittleness and TOC
2) optimizing well designs and geo-steering through detailed, seismically derived structure maps
3) optimizing the stimulation program by understanding the variances in rock properties within the shale zone and the areal distribution of Young's Modulus, Poisson's Ratio, and local stress regimes.

Method
To address these challenges, a 67 square-kilometer, wide-azimuth, multi-component (3C3C) seismic survey was recorded in central Pennsylvania. Its purpose was to determine the effectiveness of modern 3D3C seismic data in extracting certain rock properties from the Marcellus Shale to identify ‘sweet spots' and optimize both the drilling and stimulation programs.

Seismic attribute volumes that reflect elastic properties were generated from the seismic data along with geometric attributes of curvature and coherency. Multiple inversion techniques were also investigated, including a P-wave simultaneous inversion and a joint PP/PS inversion to document the value derived from the 3D3C seismic data. All elastic and seismic attribute volumes were calibrated to the existing subsurface data including wireline data, core data, microseismic events and production information for use in ‘sweetspot' prediction.

Conclusion
Upon completion of the project, this multi-discipline integrated work team concluded the 3D3C seismic data enabled us to identify major fracture lineaments and predict a set of rock properties from composite inversions and attribute volumes within the Marcellus shale. Acknowledgements

We would like to give our sincere thanks to both Anadarko Petroleum and ION Geophysical for providing permission to give this talk.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012